Charger Issues (Alternate Charger)

Discussion in 'Huawei Ideos S7 Accessories' started by lemmyslender, Feb 7, 2011.

  1. lemmyslender

    lemmyslender Member

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    I've tried using a couple different chargers, but none seem to charge my S7 as fast as they should. It seems like they are being limited to 500ma somehow.

    I made a usb cable using an old micro usb, cut the end off, and soldered on a adaptaplug extension and used the adaptaplug "G" plug. So basically, I can charge from any usb based source.

    I'm using Battery Info Widget, which shows estimated to to full charge. For instance, if the S7 is about 75% and I plug it in using the stock 2Amp adapter, the widget shows about 30 minutes to full charge.

    Now, if I plug into a different adapter with a usb port for charging, the widget shows 1-2 hours to full charge. The percentage charge also goes up correspondingly slower.

    I've tried a generic usb car adapter (~500 ma), a usb wall plug (~800ma), Griffin dual 1amp usb car adapter, scosche usb ipad wall adapter (2.1amp), scosche usb ipad car adapter (2.1amp), iGo usb wall adapter (~800ma).

    With the Griffin and Scocshe adapters I used a portable hard drive cord to plug into both ports. That should have given me at least 2amps being supplied to the S7. However, it still charged as if it were only using about 500ma.

    Anyone else having similar issues using non-oem chargers?
     
  2. pa49

    pa49 Senior Member

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    The current draw from any standard USB port is set by the USB consortium as a nominal 500mAh so charging the S7 in this way will be slower. The device needs a 2mAh rated source to optimaly and efficiently charge. Anything less and there is the risk of heat build up and power source failure which has been reported in another post. Always charge from as high a current rated source as possible.
     
  3. lemmyslender

    lemmyslender Member

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    Thanks pa49. That's what I'm trying to do. For instance, the scosche chargers both have 2 usb ports. 1 port is rated at 1 amp, the other port is rated at 2.1 amps. The chargers are designed specifically to support the ipad (which draws 2 amps as well). reVIVE II - Dual USB Car Charger for iPad

    The charger should be capable of supplying the required power (2 amps). However, the S7 still charges slowly.
     
  4. pa49

    pa49 Senior Member

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    That setup should have no problem charging the S7 properly!
    I use something similar.
    My cable was made up from a coiled lead desoldered from a cheap motorola car charger ( the older units use the correct power tip plug end for the S7 ) that I bought in a dollar store ( I think it was from Family Dollar ). I added the USB plug end with solder and shrink tube and use it with an Energizer XPAL 18000 LiPo battery pack and the charging rate is as the mains power charger.
    Something is regulating your charge current and I wonder if it could be due to on board circuits in the charger adapter although I can't for the life of me see why that might be unless there is something specific about the 2.1mAh port that is required for iPad charging and interfering with higher power for other devices. The blurb on your link is very specific that one is for iPad and the other for additional devices!
     
  5. lemmyslender

    lemmyslender Member

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    Well, perhaps it's time to re-flash, though I can't see how that would make a difference.

    As near as I can tell, chargers for ipod/ipad need to show 2.8v on data+ and 2.0v on data- (usb) for the ipod/ipad to recognize it as a charger. Near as I can tell, this is accomplished by adding a couple of resistors (4). I'm pretty certain the charger(s) can't tell what is being charged, and lower the power accordingly.

    I did notice yesterday Scocshe now has the same charger for the Galaxy Tab. The only difference should be the lack of the resistors to show the correct voltage on the data lines to allow the ipod/ipad to charge. I suspect the 2.1A socket has the resistors and the 1A socket may not.

    I would think using a y cable for power should get me close to 2A even if the sockets are each only supplying 1A. But the charging rate doesn't change.

    Very strange.
     
  6. pa49

    pa49 Senior Member

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    Yup, that explains it!
    You get 500mAh until it sees the iPad and then the circuit switches into 2.1mAh mode.
    If the Galaxy powers through the micro USB port then you may find the circuits switch with that model as well.
    This could be the exact reason for Huawei powering through a separate power socket.
     
  7. lemmyslender

    lemmyslender Member

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    Actually, I hope that is not the case. These don't appear to be smart chargers, in that there is any logic tied to the data lines. They just provide the proper (non-standard) voltage on the data lines. That indicates to the iphone/ipad that it is ok to pull more than 500ma.

    For non i-devices, offering 2A wouldn't hurt anything, the device would just pull power as required. It would seem strange to add complexity and cost to the charger to verify that the attached device is an i-device. The tear-downs of official apple chargers apparently don't verify the device. They only have the resistors.

    Off to radioshack after work to buy another adaptaplug extension. I'll test a direct connection to the charger with something other than a usb cable. Also, I guess I can try shorting both to ground (I've left them open/floating and shorted to each other).

    The only other thing I can thing I can think of is that the charger seems to be putting out about 4.98v. I wonder if the S7 dectects a "low voltage" condition and decreases the power it is drawing? I haven't checked the voltage from the stock charger.

    ***EDIT***

    Instead of working, I've been thinking, and doing a little googling to refresh my memory.

    Amps (I) are related to Voltage (V) by I=V/R where R is resistance.

    Smaller diameter wires have larger resistance than larger wires, and longer wires have larger resistance than shorter wires.

    Thinking about my homemade cord, the power (red/black) wires are pretty skinny. About the same size or very slightly larger than the data wires.

    Now, if the power wires were twice as thick, at the same length, the resistance is about 1/4 of the thinner wires. So what I can infer from this is that if I use a charger that was designed for use with thicker wires, and use the thinner wires in the cord, the resistance is increased by a factor of 4. This means the amps are reduced by a factor of 4.

    So a 2 amp charger using thinner wire would potentially output only 0.5 amps.

    The Griffin dual 1 amp car charger came with a cord for ipod/iphone charging. Cutting it apart reveals significantly thicker red/black wires. So I'll wire up that cable and see if charging improves.
     
    Last edited: Feb 8, 2011
  8. lemmyslender

    lemmyslender Member

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    Got a new adaptaplug extension and quickly wired to the ipod/phone usb cable. Tested on the way home. Definitely made a difference.

    Charging with either Scosche chargers (2.1A) is now similar to charging with the stock charger. In the car it now charges noticeably while using navigation on the default (when you plug it in) brightness. It also charges noticeably on the wall charger will playing Angry Birds on the default brightness.

    I'll give it a day or two for testing to make sure before I solder anything this time.

    I should note, charging with the previous cord is still much slower.
     
  9. pa49

    pa49 Senior Member

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    Interesting!
     
  10. thek135

    thek135 Member

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    pa49, do you know what Motorola phones use this plug?
     
  11. skoster

    skoster Member

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    Trust me, the resistance of the wires is negligible in the circuit, the amperage is not in any way regulated by the wire size. I'm a ISCET certified electronics tech.
     
  12. lemmyslender

    lemmyslender Member

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    I'm inclined to believe you. However, I have 2 cables with thicker wire that charge at the same rate as the stock charger. I also have several cords with significantly thinner wire that charge at a much slower rate. All were checked using the same charger under similar circumstances.

    Frankly, I don't really believe what I wrote either, but then I'm at a loss to explain the difference in charging rates. Can you offer any explanation for this phenomenon?

    While it may not be applicable in this case, I am pretty sure that the size of the wire influences the amount of amperage it can handle.
     
  13. cansat

    cansat Member

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    Leyendo en un foro del s7 comentaban que el cargador de coche del navegador Magellanes era compatible, buscando por ebay me pedi este:
    Magellan 5V 2A Maestro 3100 4000 GPS Car Charger en venta en eBay.es (finaliza el 10-may-11 08:51:50 H.Esp)

    Me acaba de llegar y lo he probado y va perfectamente, tiene alimmentacion 5V 2A como el cargador de pared y la cabeza va perfecta.

    Saludos

    Reading in a forum of s7 they were commenting that the loader of car of the mariner Magellanes was compatible, looking for ebay me pedi for this one:
    Magellan 5V 2A Maestro 3100 4000 GPS Car Charger en venta en eBay.es (finaliza el 10-may-11 08:51:50 H.Esp)
    It has just come to me and I have proved it and it goes perfectly, has alimmentacion 5V 2A as the loader of wall and the head goes perfect.

    Regards

    [​IMG]
     
  14. skoster

    skoster Member

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    Size of wire absolutely influences the amount of amperage it can take (with the caveat that both diameter of wire and length of the wire run play into this), you'll burn the wire up if you try to run too much amperage through wire which cannot handle it. However, the limiting factor in a *well designed* circuit will not be influenced by normal wire runs.

    My guess is that the circuit designer used a linear voltage regulator with thermal protection and, when you try to draw more amperage through the thin wires than they can handle, thermal runaway happens (the wire tries to burn up) and the thermal protection clamps the current. This is a common crappy design issue I see in imported Chinese electronics.
     
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  15. lemmyslender

    lemmyslender Member

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    That was my original guess (although not as clearly stated) and is the likely answer. I had tried a couple of different ways with different chargers ending in the same result. I had used some brand name stuff with similar results. Either way, the thinner wire seems to be the one of the factors in slower than expected charging.

    I just wanted to point out that using thicker wires resulted in faster charging (thank you for the better explanation). With the S7's smaller battery, charging time can be important if charging availability is limited (say in-between flights in an airport). With the right charger and a good cord, you can substantially reduce the charging time, and increase usable time.
     

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